A new high-resolution electron probe has been built for scanning microscopy studies. The probe has a final lens with a focal length of 0.8 mm, a spherical aberration coefficient; of 0.4 mm, and a chromatic aberration coefficient of 0.5 mm. A lanthanum hexaboride cathode is employed with a maximum brightness of 1.5×107 A/cm2 sr at 75 kV. The cathode operates satisfactorily at a pressure of 10−6 mm Hg. The theoretical minimum beam size for the instrument is 5 Å. Transmission scanning electron micrographs with a beam current of 1×10−12–3×1012 A indicates that close to this value is obtained in practice.